1. Field of the Invention
The present invention pertains to an image shake correcting optical apparatus, and more particularly to an image shake correcting optical apparatus that can maintain at a prescribed position a correction optical system that can correct image shake that occurs due to movement of the optical apparatus.
2. Description of the Related Art
Conventionally, in the camera field, as a means to correct image shake in the focal plane due to the shaking of the camera user's hands when a photograph is being taken, a correction optical system is known in which a correction lens is located behind the photo-taking lens and is driven within a plane perpendicular to the optical axis of the camera to decenter the correction optical system. A lens apparatus equipped with this correction optical system has a construction in which a dedicated actuator to drive the correction lens in prescribed directions is incorporated in the lens apparatus, the amount of camera shake is detected by a shake sensor such as an angular velocity sensor, and the correction lens is driven by means of the detection signals from this sensor.
As the actuator that drives the correction optical system, a moving coil actuator has been proposed in which two electromagnetic coils are located in a plane perpendicular to the camera's optical axis, and yokes and permanent magnets are located on the fixed frame of the lens barrel so as to correspond to the electromagnetic coils.
Because this moving coil actuator is easy to control, it is appropriate for a drive mechanism for the correction lens that corrects image shake, but if the supply of current to the electromagnetic coils is cut off, the correction lens cannot be maintained at that position. As a result, in order to maintain and fix the correction lens at a prescribed position, a separate fixing mechanism by means of an electromagnetic means has been used, including the driving of the plunger using a solenoid.
However, because such a fixing mechanism based on an electromagnetic means is large and heavy, it makes the optical apparatus large as a whole and increases its cost.
Where the fixing mechanism is based on an electromagnetic means, disengagement of the correction lens fixed at a prescribed position takes place instantaneously, and therefore, when disengagement occurs, the correction lens may move inadvertently, and the camera user may experience a sense of unease during the movement of the screen.